1. Field of the Invention
The present invention relates to a stator of a rotating electric machine, and particularly relates to a stator of a rotating electric machine in which a coil winding is wound inside a slot.
2. Description of Related Art
In order to make a rotating electric machine compact and have technical advantages, it is necessary to wind a coil in an efficient manner and reduce loss such as copper loss or iron loss. Japanese Patent Application Publication 2009-232607 (JP 2009-232607 A) discloses that a flat wire having a concave portion and a convex portion is used as a stator winding of a rotating electric machine and that flat-wire coils are disposed in a slot such that the convex portions and the concave portions of the adjacent flat-wire coils are fitted with each other, thereby increasing a space factor of the coils in the slot.
It is described in Japanese Patent Application Publication 2011-210638 (JP 2011-210638 A) that a magnetic body layer that serves as a wire used for a coil of an electromagnet is provided on a surface layer of a conductor to increase an attractive force of the electromagnet. In an embodiment where this wire is used as a winding for a distributed winding coil of the stator in the rotating electric machine, the plural wires having a circular cross section are accommodated in a single slot.
It is disclosed in Japanese Patent Application Publication 2008-236924 (JP 2008-236924 A) that thickness of an insulating layer coated on a flat coil wire or a type of an insulating material is changed between a coil end portion and a slot portion to reduce the size of the rotating electric machine. It is also described that, as a field buffer layer that reduces a steep surge voltage of an inverter, an electroconductive polymer layer or a layer of epoxy resin or the like in which a conductive filler or a semi-conductive filler is mixed is provided on a surface of a coil conductor or a surface of the insulating layer.
Although the space factor can be increased with use of the flat wire that has the concave portion and the convex portion, eddy-current loss that is caused by a leakage magnetic flux may be increased due to a reduced resistance value of the conductor that consequently promotes a current flow. The eddy-current loss can be reduced by providing the magnetic body layer on the surface layer of the conductor. However, the space factor is reduced by the thickness of the magnetic body layer.